1. Field of Invention
The invention relates to an interlace method and a method for generating an interlace algorithm and, in particular, to a method for generating an interlace algorithm, which can generate an adaptive tuning de-interlace algorithm, and an interlace method, which can utilize the adaptive tuning de-interlace algorithm.
2. Related Art
The video industry has been progressed form the analog age to the digital age, so the present video processing device must equip the function for transforming the analog signals into digital signals. Regarding to the scan standard of present analog televisions, the most popular standards includes the Television Standards Committee (NTSC) type and Phase Alternation by Line (PAL) type. In the NTSC type, 525 scan lines are used to construct a frame (or a screen), and 30 frames (screens) are displayed per second. Herein, every screen is displayed by a way of interlace scan. In other words, after the first scan line is displayed, the consequential scan line to be displayed is not the second scan line but the third scan line, and then the fifth scan line, seventh scan line, and so on are displayed in sequence until the 525th scan line. After the 525th scan line, the second scan line is consequentially displayed, and then the forth scan line, sixth scan line, eighth scan line and so on are displayed in sequence. Thus, the obtained smooth and clear frames (screens) are actually interlaced by the frame of odd scan lines, the frame of even scan lines, the frame of odd scan lines, and so on. This is the “interlace scan”, and is known as an “interlacing format”.
The interlace video signals are composed of two fields, wherein each field includes the odd scan lines of the image or the even scan lines of the image. When performing the image capture, the television camera outputs the odd scan lines of the image in a flash, and then outputs the even scan lines of the image after 16.7 ms later. During the period between the odd scan lines of the image and the even scan lines of the image are displayed, a temporal shift occurs and should be positioned in a frame based system. However, this method, regarding to the dynamic image with moving properties, may cause serrations at the edge of the image. In addition, the odd field and even field are respectively constructed by half scan lines such as 263 scan lines and 262 scan lines, so that the resolution of each odd field or even field is only half of the original image, and each of the odd fields and even fields is displayed per 1/60 second. Thus, the human vision may not figure out the motion artifacts. However, once the screen is enlarged, the scan lines seem thicker resulting in the blurred screen(s).
The disadvantages of performing “interlace scan” or “interlacing format” are now solved by the progressive scan technology. The progressive scan technology is to continuously display the first scan line, second scan line, third scan line, and so on until the 525th scan line. Sixty screens are represented per second. Thus, the scan speed of the progressive scan is twice of that of the interlace scan. Accordingly, the screen displayed on the monitor is constructed with 525 scan lines, so that the screen is very fine and clear, which is the most advantage of the progressive scan. As a result, the present advanced video apparatus adopts this method for scan and display.
However, the image signals of the current NTSC system, until now, usually adopt the interlace scan method. If the screen built according to the interlace scan method is displayed with a progressive scan display system, for example that a DVD video image edited according to the interlace scan method is played and displayed on a high definition TV (HDTV) directly, the displayed screen only includes the odd field or the even field resulting in the poor image resolution (since only half scan lines are displayed). To solve this problem, the de-interlace technology is developed to provide a method for transforming the interlace scan into the progressive scan. For example, when the screen of the standard definition TV (SDTV) is transformed to that of the HDTV, a de-interlace step and a sampling step are employed to increase the original 480 interlace scan lines up to 720 progressive scan lines and to modify the misalignment while merging the interlace scan fields including the odd scan lines and the even scan lines. Accordingly, the vision-satisfied progressive image can be generated.
As mentioned above, although the de-interlace technology can solve the problem of poor resolution when the interlace scan system image displayed in the progressive scan system, a considerable situation is that the displayed image is always moving. If ignoring this and then directly merging the odd field and even field, the static image portion may get clear picture, but the dynamic image portion may be blurred and motion artifacts. As a result, the high quality screen may not be displayed. In view of the above, the de-interlace technology adopts two basic algorithms including the non-motion compensated algorithm and the motion-compensated algorithm. The non-motion compensated algorithm includes two typical linear transform technologies, which are wave and bob de-interlace algorithms. The wave de-interlace algorithm is to overlaid or wave two input fields for generating a progressive frame. Considering the static screens, the wave de-interlace algorithm can perfectly align images of different fields to obtain a clear de-interlace image without decayed. However, considering the dynamic screens, the wave de-interlace algorithm may cause obvious serrations at the edge of the dynamic image. This is because of that the dynamic screen has the temporal shift. Therefore, when waving an odd field and an even field into a frame, the image misalignment may occur caused by the temporal shift between the odd and even fields so as to generate a blurred frame with serrations (as shown in FIG. 1). In addition, the bob de-interlace algorithm is to retrieve one field, such as the even filed, and the other field, such as the odd field, is discarded. Thus, the resolution of the vertical direction of the screen is decreased from 720×486 pixels to 720×243 pixels. This image with only half resolution employs the scan lines to fill up the adjacent voids, so as to obtain an image with 720×486 pixels. The advantages of the bob de-interlace algorithm are to overcome the motion artifacts of the screen, and have smaller calculation requirement. And the disadvantage thereof is the poor vertical resolution (half of the original image), so that the fine resolution of the progressive screen is decreased.
Since the present digital versatile disk (DVD) still records the images shot with the interlace scan system, the displayed image from the DVD must be processed with an interlace procedure. When using a Hi-Fi digital TV to play the DVD, the playing device must provide an option of the wave or bob de-interlace method for transforming the interlace scan into the progressive scan. However, if the wave de-interlace method is selected, the misalignment for the moving image may occur to cause the displayed image with serrations. Otherwise, if the bob de-interlace method is selected, the misalignment for the moving image may be overcome to obtain clear and motion nature of dynamic image, but the vertical resolution for the static image is sacrificed. Therefore, between the present video playing system and digital displaying system, the image qualities of dynamic screens and static screens can be concerned properly after the de-interlace processes.